There are three principal methods of electroplating. The first and most commonly used method involves immersing the object to be plated in a bath of electrolyte solution and passing an electrical current between the electrolyte and the object. According to a second method the object to be plated is immersed in a bath but no electrical current is used; this is referred to as electroless plating. In a third method, known as brush plating, no plating tank or bath is used and instead the electrolyte solution is applied to the surface of the object to be plated by means of a brush which also acts as an electrode for conducting current through the electrolyte to the object.
Many objects which need to have a plated surface either for purpose of protection or for decorative appearance, or both, cannot be conveniently transported to and immersed within a plating tank. As one example, bathroom plumbing fixtures frequently have metal parts that are permanently installed and cannot be conveniently removed; hence if the entire set of metal parts is to be refurbished by means of electroplating, it is necessary to accomplish the electroplating at the site.
As is well-known, brass is not a pure metal but is an alloy of copper and zinc, usually containing more than 50% copper. A characteristic of brass is that its surface when exposed to air tends to corrode and become discolored. Therefore, it has been a common practice to finish the surface of a metallic member by covering it with brass plate, and then in turn to cover the brass plate with a thin layer of transparent plastic material. This does provide effective protection on a temporary basis, but when the plastic coating wears through, as it eventually does, the brass plating is then exposed to air and becomes discolored.
A need has therefore developed for applying a decorative brass finish that will not corrode or discolor. The problem is particularly acute when the nature of the object to be plated is such that it cannot be conveniently transported to and immersed within a conventional plating tank.